Method of impregnating with a compound



May 7, 1929. COLEMAN 1,711,774

METHOD OF IMPREGNATING WITH A COMPOUND Filed May 26, 1925 Patented May7, 1929.

UNITED STATES PATENT OFFICE.

CHARLES E. COLEMAN, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO F. J'.

STOKES MACHINE COMPANY, OF TION OF PENNSYLVANIA.

PHILADELPHIA, PENNSYLVANIA, A, CORPORA- METHOD OF IMPREGNATING WITH ACOMPOUND.

Application filed-May 26,

The present invention has to do mainly with improving the dielectricqualities of high tension electrical cables after they have been wrappedwith paper or equivalent hinder or wrapper, by saturating them with adielectric compound in a melted or liquid state. The compound usuallyincludes vaseline and resin. However, the invention is applicable inwhole or in part to saturating .10 or impregnating other material. withthe same or with other substances.

The principal objects of the present inVention are, first, to materiallyand substantially reduce the time consumed in the process; an

F second, to improve the dielectricproperty or quality of the cable bypermitting the compound to set or solidify under such pressure as willprevent the occurrence of voids due to shrinkage.

The invention will be claimed at the end hereof but, generally stated,it may be said to comprise the method of impregnating material with amelted or heat softened compound which consists in removing the moistureand air from the material to be impregnated by subjecting it to heat andvacuum in a closed chamber, impregnating the dried and air freedmaterial by subjecting it in the chamber to the action of the melted orheat softened impregnating compound under pressure, and cooling theimpregnated material by subjecting the impregnating compound, tocirculation and heat exchange with or without agitation.

The invention also comprises the improvements to be presently describedand finally claimed.

In the following description reference will be made to the accompanyingdrawing forming part hereof and in which Figure 1 is atop or plan view,and

Fig. 2 is an elevational view with broken away.

In the drawing 1 and 2 are vessels or chambers to which heat is appliedas b jackets 3, and they are adapted to be close The chamber 1 is a tankin which the impregnating compound is prepared, mixed and melted. Thechamber 2 is adapted to receive the material to be impregnated, forexample, high tension electrical cable wound on drums adapted to beaccommodated by the vessel or chamber 2. 4 is a vacuum con: nection forthe chamber 2. 5 is a cooler parts 1925. Serial No. 32,909.

illustrated as a heat exchanger shown as having a jacket 6 for coolingfluid such as d connection 14: from the bottom, of the chamber or vessel2 to the bottom of the cooler or heat exchanger 5, and from the top ofthe latter to the top of the vessel or chamber 2. This connection 14includes a pump 15, and a valve 16, and it may be fitted with a strainer17.

In the practice of the invention the material to be impregnated, forexample high tension electrical cable wound upon a drum, is subjected toheat and vacuum in the closed chamber 2. For this purpose use may bemade of the vacuum connection 4, and the purpose is to remove moistureand occluded air from the material so that when the impregnating orsaturating compound is introduced it can enter the material without airresistance. The vacuum connection may be closed and the dried and airfree material in the vessel or chamber 2 is subjected to the action ofmelted or heat liquefied impregnating compound under liquid pressure.For this purpose the mixed and melted impregnating material in the tankor vessel 1 is pumped by the pump 11 into the vessel or chamber 2, whereit submerges-the material to be impregnated and where a pressure of,without limitation, 80 to 100 pounds will be built up. The liquidpressure thus. applied may be regulated by adjustment of the reliefvalve13.which operates to provide limited flow from the pressure to thesuction side of the pump. The liquid ressure operates to accelerate therate 0 impregnation and it has the advantage that moisture is notintroduced as would be done der pressure through the cooler or heatexchanger 5 where it gives up its heat to the cooling fluid and where itis prevented from accumulating on the heat exchange wall by theagitation or scraping action of the element 7. Inasmuch as the heatexchange surface is kept free from accumulations of solidified compound,the heat exchange is facilitatedand the time required for coolingshortened. Impregnating compound at the end of the operation may bereturned to the mixing tank 1 by reversing the direction ot operation ofthe pump 11. Of course the heat may be turned off from the vessel 2during the cooling operation.

There is an advantage in cooling the im-'- pregnating compound Whileunder pressure greater than atmospheric although many persons may notelect to employ it, and that advantage may be described as follows: Bythe vacuum, immersion and pressure step the Wrappings of paper or othersubstance of the cable are impregnated, and as the impregnating compoundsolidifies by cooling it tends to shrink and produce voids such as mightand probably would impair the quality of the cable. However, by keepingthe impregnating compound under pressure as it solidifies, as in myinvention, the formation of objectionable voids is obviated and theimpregnation is complete throughout, because any loss due to shrinkageis olfset or made up by fresh compound supplied under pressure.

It will be obvious to those skilled in the art to which the inventionrelates that modifications may be made in details ofconstruction andprocedure and in mere matters of form Without departing from the spiritof the invention which is not limited as to such matters or otherwisethan the prior art and the appended claims mayrequire.

I claim:

1. In the method of impregnating material by subjecting the material ina closed vessel to vacuum action and to an impregnating compoundrendered fluid by heat, the improvement which consists in applyingmechanical pressure to the fluid compound and thus opposing theintroduction of moisture, cooling the material by circulating thecompound under mechanically applied pressure into and out of the vesselin a path external to the vessel, and cooling the circulating compoundin said external path by heat exchange.

2. In the method of impregnating mate rial by subjecting the material ina closed vessel to vacuum action and to an impregnating compoundrendered fluid by heat, the improvement which consists in applyingmechanical pressure to the fluid compound and thus opposing theintroduction of moisture, cooling the material by circulating the,compound under mechanically applied pressure into and out of the vesselin a path external to the vessel, and cooling the circulating compoundin said external path by heat exchange and agitation.

CHARLES F. COLEMAN.

